There are many possible ways to provide a roof for a structure. One possible way to roof a structure is through the use of roofing panels. The art of roofing structures with roofing panels has advanced to the use of standing seam metallic roofing panels. Standing seams are formed when raised longitudinal edges of roofing panels are joined together to form a longitudinal ridge running from the peak to the eave line of the roof.
Standing seam metallic roofing panels are normally manufactured from GALVALUME.TM. steel and may be painted or coated with a protective film to protect them from oxidation or corrosion. However, other materials may easily be used to form panels of sufficient strength and flexibility so as to be useful in roofing a structure. The individual panels may vary in width from one to two feet, and may be up to forty-five feet in length.
In erecting a structure, walls or columns of the structure are first built. Rafters, which form the primary roof support, are carried by the walls or columns. These rafters usually span the width of the structure. Joists or purlins are located across the rafters and are supported by the rafters. Joists or purlins are normally installed perpendicular to the rafters, thereby defining the roof line. The purlins normally extend along the length of the building. Insulation may conveniently be laid across the purlins or joists.
A standing seam roofing system may be installed on the purlins. Roofing panels are joined together along adjacent longitudinal sides in a male/female relationship to form the standing seams.
In the past, various devices have been employed to attach the standing seam roofing panels to the purlins. It is well known in the art that it is advantageous to support and attach the roofing panels to the purlins along the standing seams formed by the raised longitudinal edges of adjacent roofing panels.
A clip is a device used to support the roofing panels, and attach the panels to the purlins and hence the structure itself. However, the clips known in the art have all been characterized by a common drawback. All of the clips according to the prior art are flawed in that they do not provide for sufficient flexibility or movement of the roofing panels relevant to the purlins.
During construction of the roof, and periodically after the roof has been completed, the roofing panels on the roof experience loads which cause the panels to move rotationally relative to the normally rigid purlins. Typically, these loads are caused by workers walking on the roof but may also be caused by environmental loading such as that caused by wind, rain, or snow. Further, when metallic roofing panels are used, the roofing panels will expand and contract due to climate changes. This constant thermal expansion and contraction causes the roofing panels to move longitudinally, or translationally, relative to the rigid purlins positioned below.
Further, during assembly of the standing seam roof on a structure, the roofing panels will often be displaced by workers assembling the panels. This constant displacement, or jostling, may cause the panels to bend or destroy the clips.
Also, when purlins or joists are installed on a structure, they are sometimes not positioned in proper alignment with the other purlins. Further, according to industry standards, as set forth in the Metal Building Systems Manual published by the Metal Building Manufacturers Association, the flanges of the purlins may be manufactured up to 3.degree. out of the square with the web of the purlins. Therefore, the flanges of the purlins may be manufactured to be between 87.degree. and 93.degree. relative to the web. This industry accepted tolerance, by itself, and especially when coupled with improper alignment of the purlins on the stucture itself has, in the past, caused serious problems when a standing seam roofing system is later installed on the structure.
The problem being that it is very difficult to attach a standing seam, formed by two adjacent roofing panels, to a flange of a purlin that is neither perpendicular to the standing seam, nor positioned in a plane parallel to the ridge of the standing seam. Even if the standing seam is attached to the purlin, it will be incapable of accommodating expansion and contraction experienced by the metallic roofing panels.
One solution, now well known in the art, has been provide a clip, a portion of which is able to slide back and forth relative to the purlin. However, these sliding clips have also been marked by serious disadvantages. If the purlins supporting the roofing system are misaligned or manufactured with the web of the purlin being out of square with a flange of the purlin, as outlined above, these known sliding clips have been incapable of any sliding movement whatsoever. Typically the friction experienced in the moving pieces of these prior-art, sliding clips has been so great that for all purposes they fail to slide once the roof is in place. Therefore, when the roofing panels experience loads, or movement due to thermal expansion and contraction, the panels bend the clips, or the clips fail to move with the panels and destroy sealant positioned between the panels, thereby causing the roofing system to leak.
Thus, the prior art clips have demonstrated various disadvantages which have heretofore not been overcome.